Blast fence



March 24, 1964 B. s. LYNN 3,126,176

BLAST FENCE Filed Sept. 11, 1962 2 Sheets-Sheet 1 FIG. 4

FIG. 2

In ve n 1 o r:

Bernard Stanley Lynn his orney March 24, 1964 B. s. LYNN 3,126,176

BLAST FENCE Filed Sept. 11, 1962 2 Sheets-Sheet 2 Inventor:

Unite Staes 3,126,176 BLAST FENCE Bernard Stanley-Lynn, 19451 Black Road,

Los Gatos, Calif. I Filed Sept. 11, 1962, Ser. No. 222,863 11 Claims. (Cl. 244-114) This invention relates to blast fences, and has for its principal object the provision of a blast deflecting surface, supported by a series of spaced angle irons each rolled to an arc having a radius roughly approximating the height of the blast fenceso that the surface will be a portion of a cylinder and will direct a horizontal blast to a vertical direction. 1

A second and important object of the invention is to form the blast deflecting surface of corrugated metal with the ribs and valley running horizontallyrthat is at right angles to current accepted practice.

A further object is to preserve the aerodynamic advantages of the blast fence described in my Patent No. 2,974,- 910, dated March 14, 1961, while providing greater structural integrity and longer life of the fence by eliminating the tendencyto vibrateunder present-day heavier blasts from the larger jet engines with afterburners. This object is achieved by giving additional rearward support to the blast deflecting surface at all points along closely spaced bands, each of which is fixed at or near ground level at the leading edge, with additional provision for transmittal of blast loads directly to ground from, one or more points on supporting bands. Another important object of the invention is the novel manner in which the relatively uniform blast load is concentrated along uniformly spaced band supports, and then economically transmitted through these bands and rear support struts into the ground through concrete piers poured in auger dug holes; thereby entirely eliminating need for reinforcing bar, forms, massive concrete slab and expansion joints as required by my previous Patent #2, 974,9l0. By this novel concentration of blast loads only a fraction of the number of leading edge anchor bolts are required with a resultant great saving in materials and labor.

A still further object of the invention is to reduce the cost of blast fences by increasing the section modulus of the blast deflecting surface, so that a thinner gauge of steel preferably with deeper corrugations than usual may be used, provided the ribs and valleys, contrary to present practice, run horizontally rather than vertically. While it is true there will be a projection of the now-transverse ribs of the corrugated steel strips into the blast stream, thus slowing down the speed of the stream, this is more than compensated by the diversion sideways of a part of the air stream which then flows over itself close to the ridges of corrugations.

In the drawings:

FIGURE 1 is a side elevation of a preferred form of fence.

FIGURE 2 is a front view, p artly broken away.

FIGURE 3 is an enlarged detail of the upper extremity of FIGURE 1 with portions ofthe end plate removed.

FIGURE 4 is an enlarged detail roughly on line 44 of FIGURE 1.

FIGURE/3 isa side elevation of a smaller and simpler 7 3,.l2hllh Patented Mar. 24, I954 approximately the nominal height of the fence, in this particular case 8 feet, so that the blast surface is a portion of a cylinder and changes the horizontal blast through degrees to vertical.

The forward end of each curved angle iron vane support 11 is held on an angle iron clip 14 held at ground level by an anchor bolt 15 embedded in an 8-inch deep concerete slab 16 preferably having two spaced mats of No. 4- reinforcing bars 17 on 12-inch centers both ways.

.Such slab footings should be'slightly wider than the height of the fence and run the length of the fence, which may vary, usually from 4 feet to 8 feet in height.

It is sometimes'convenient to raise the forward or leading edge of the fence just enough, from one to three inches, to permit dirt and debris to blow through the slight opening thus createdand consequently to avoid the accumulation of such material in front of the fence. This is readily accomplished by bolting corrugated steel vanes to the curved angle supports starting at a point more than one inch as at 49, out less than three inches above the ground surface. Thus the bottom edge of the lowest corrugated vane becomes the leading edge of the blast deflecting surface, and said edge is parallel to the ground surface along length of fence.

In order to give additional firm support to the rear of the central portion of the blast deflecting surface I secure an angle iron anchor clip such as 2% to an anchor bolt 21 embedded in the concrete base and spaced from similar forward bolt 15 by a distance which may be considerably less than the height of the fence when the concrete slabs are used, but which should equal or exceed the height of the fence when cylindrical piers are used, as in FIGURE 5, as this spacing will minimize or completely eliminate any tendency of the fence to overturn upon receiving an exceptionally heavy blast as the overturning moment then becomes zero.

Struts 23 and 24 of suitable angle iron are secured to the angle irons vane supports llrat selected points, preferably by single bolts such as 25 and 26 for convenience in erection and removability to a different location. These two struts minimize the previous large unsupported surface between the leading edge 22 of the fence and the upper or trailing edge 32. The connection between strut 24 and the angle iron 11 is located about centrally of the length of the curved vane supports, whereas the connection 25 of strut 23 may be as far from the top of the fence as two feet as the trailing edge 32 is supported by the cantilever overhang of the angle iron vane support 11. The longer strut 23 may be of 2 /2" X 2 /2" X A size, and the lower strut 24 may be of slightly smaller size, about 2" x 2" x A" with the spacing to be determined by the center of pressure of the blast load.

It will be seen that the parallel angle irons ll. spaced apart only 36 and each braced to the concrete slab 16 form an exceptionally sturdy mechanical support for the galvanized vanes of the blast deflecting surface which may be assembled with an overlap if desired so that the top edge of each of the 26-wide panels or strips is visible from the front or blast receiving side of the fence. For commercial lighter duty the curved supports may be spaced 4-8" apart.

The vane supports, while preferably of angle irons, may be of other flanged rolled stock, or may as shown in FIG. 7 be of curved solid steel bars such as 1111, a convenient size being /2" x 2 /2. The central hole in the wide face is to receive the bolt 26 of the strut 24 or the bolts holding the horizontal tie 47 and the holes in the upper narrow face of the rolled bar stock are drilled and tapped to fit cap screws passing through washers 3t) holding the blast deflectingsurface 10 in place.

The blast deflecting surface 10 is preferably made of strips or panels of corrugated steel of 16-gauge sheet with standard 2.66 spaced corrugations, the latter however being deeper than the usual /z; being preferred. These corrugated sheets 2'7 and 28 (FIG. 2) are bolted to the angle irons 11 spaced preferably 36 to 48" apart and are secured by /8 headed bolts pressing against a deformed flat washer 30 (FIGURE 3) in a valley and having at the rear a star loclrwasher 31, where angle iron vane supports are used, thus securing a positive connection between the corrugated sheet or panel 27 and the arcuate supporting angle iron ill.

At each side end of the fence it is preferred to have an optional end plate 34, as these prevent spilling of the air blast laterally around the fence. To increase structural rigidity the straight margin of each end plate 34 is bent at right angles twice as at 35 and 36 to provide a built-in channel 37 which preferably is about 1% wide and has a lip of A".

A simpler form is shown in FIGURE 5 illustrating a 7-ft. fence. The rolled iron vane support 11 is of the same size as in the preferred form, and like that is formed as an arc of a circle having about a 96-inch radius. The wider 3" flange 4t faces rearwardly and the shorter 2" transverse flange is perforated by holes or slots to receive bolts, which preferably are slightly smaller in diameter than the holes. When the panels 27 and 28 of corrugated steel are bolted in place they conform to the curvature of the vane supports ll as shown by the rear flange 40. In this modification a strut 41, reasonably similar to strut 23, is used and this brace for a 7-foot fence is about 65 inches long but is used only in connection with the piers shown in this figure as replacing the far more expensive concrete slabs. Each of the piers 44 is formed in an auger-bored hole which is filled with concrete 45, in which an anchor bolt such as 21 has been set; to which is bolted an anchor clip 26. In each case the centerline of the anchor bolt is located considerably nearer to the front edge of the cylindrical pier than to the axis of the pier, the diameter and the depth both being about 18'.

In FIGURE 7 the strut or struts shoring the intermediate portion of the vane supports 11 are omitted and the angle irons ila and 11b bolted together at their upper ends 46, may be rigidly secured together by the horizontal tie 47, and each have their lower ends fast to a concrete slab 48 or to a pier. This construction results in some economy as compared to using two single blast fences with two sets of rear struts, and it does have the additional advantage that the velocity of the deflected blast is augmented by the induced flow of air upward across the smooth curve on the upper portion of the opposite side of the blast fence.

The unsuspected structural advantages of using the corrugated panels with the ribs and valleys running horizontally cannot be over-emphasized, and may be summarized as follows:

(1) The full value of the very high section modulus of corrugated steel as compared with flat steel can be utilized in resistance to bending by the blast. For example, the section modulus of flat l2-gauge steel is only about that of 14-gauge corrugated steel. This means that the corrugated steel while of lighter weight still has about 27 times the resistance to bending of the heavier l2-gauge flat steel.

(2) By bolting the corrugated metal in place with the ribs positioned horizontally, and using a deeper than standard corrugation the deflecting surface can be shown to have a greater resistance to bending although a thinner gauge of steel is used, thus resulting in a lower cost of manufacture. For example, the section modulus of l6-gauge steel with standard 2.66" x /2 deep corrugation is .0071 cubic inch per lineal inch of horizontal projection about the neutral axis; but if a 2.66" x ,41" deep corrugation is used the section modulus is increased to .012 cubic inch per lineal inch, which is greater than the section modulus of 14 gauge standard 2.66" x /2" corrugated steel which is .0087 cubic inch per lineal inch.

4 Thus we can use a 16-gauge sheet with 2.66" x corrugations and obtain greater resistance to bending than if we used the heavier and more expensive l4-gauge standard corrugation. This great strength with economy can only be realized if the corrugations are bolted horizontally; because if a deeper but thinner section were used in the structure shown in my Patent No. 2,974,910, it would act like a sail and the corrugations would tend to elongate or unfold like an accordion, as the sheet or panels in that configuration are unsupported except at the leading and near the trailing edges.

(3) The aerodynamic resistance of the corrugations which project into the blast stream is of no disadvantage because the projection into the blast is only about while the blast stream itself may be up to 20 feet thick; thus the slowing down of the blast by the corrugations is insignificant and if anything may be an advantage as the air will shear and flow over itself a short distance from the corrugations which act as vortex generators at high blast velocities.

(4) A marked and unexpected economy is realized. Reference to Patent 2,974,910 will indicate that when corrugations run vertically, panels must be fastened to ground by anchor bolts spaced 8 apart; but when corrugations run horizontally, the load is conveniently transmitted to curved vane supports which may be spaced as much as 36" or 48 apart. Thus the number of anchor bolts at the leading edge is reduced from one every 8" to one every 3 or 4 feet, thus effecting a great economy in anchor bolts as well as in labor.

What I claim is:

1. In a blast fence adapted to be installed on a ground area to receive and deflect the blast from an aircraft power unit of the jet type with afterburner, means forming a substantially impervious blast deflecting surface smoothly curved to be concave as viewed from the source of the blast, the curvature of said surface being such that a jet blast directed against the surface is directed upward from the upper edge of the fence, and a deflecting surface supporting structure; said means being of corrugated material with the ribs and valleys of the corrugations in horizontal planes and having a leading edge proximate the ground and an upper discharge edge in rear of the leading edge; said supporting structure comprising a series of uniformly curved, substantially parallel, rolled steel structural members to which are secured at closely spaced intervals along their lengths, said corrugated material;

each rolled steel structural member being secured to the ground at its forward leading end, and being secured to the ground at a single point behind said leading end through a portion of said supporting structure comprising at least one sloping shoring strut fastened to the rolled steel member, whereby the pressure of the blast is transmitted uniformly to the ground at two spaced points per each rolled steel structural member, that is, one point at the front of each rolled steel structural member and the other point at the rear of each sloping shoring strut, and said horizontal arrangement of the valleys of the corrugations produces a vortex generator effect which eliminates vibration.

2. The blast fence of claim 1 in which the rolled steel members are spaced apart a distance less than the height of the fence and the horizontal distance from each lower leading edge to the rear end of the companion shoring strut is at least equal to the height of the fence whereby to eliminate the tendency of the fence to overturn upon receiving an exceptionally heavy blast.

3. The blast fence of claim 1 in which the rolled steel members are supported at their rear at a point which is at a distance greater than one-fourth of the distance from such point to either end of the angle iron.

4. The blast fence of claim 1 in which the lower leading edge of the deflecting surface supporting structure is removably secured to the ground and the rear support of each rolled steel member comprises a strut removably secured to the ground and joining the rolled steel member at a point about one-third the distance below the top edge.

5. The blast fence of claim 1 in which the rolled steel members are angle irons and the support is a blast fence duplicate arranged back-to-back with their upper edges secured together, their lower edges secured to the ground, the angle irons secured together about centrally by a horizontal strut and the leading edge of the deflecting surface formed by the bottom edge of the corrugated material is parallel to the ground and at both front and back is spaced from one to three inches above the ground whereby to permit dirt and debris to blow under such opening and thus avoid accumulation of such material in front of and under the fence.

6. In a blast fence adapted to be installed on a ground area to receive and deflect the blast from an aircraft power unit of the jet type, means forming a substantially impervious blast deflecting surface having an upper discharge edge and a lower horizontal leading edge, said surface being smoothly curved to be concave as viewed from the source of the blast, a series of closely spaced rearward supports curved to engage the rear of the blast deflecting surface from proximate its leading edge to proximate the discharge edge to transfer to the curved rearward supports the pressure exerted against the blast deflecting surface, and rigid members connecting the curved rearward supports to the ground in rear of the upper discharge edge, said means being of corrugated material with the ribs and valleys of the corrugations in horizontal planes, the curvature of said surface being such that a jet blast directed horizontally against the surface is deflected so as to be discharged upwardly, spaced valleys of the corrugated material being secured to the curved rearward supports with the rears of intermediate valleys resting loosely upon the curved rearward supports, whereby pressure against the blast deflecting surface is transmitted successively and evenly to the curved rearward supports, to the rigid members and to the ground.

7. The blast fence of claim 6 in which the corrugated material is supported by a series of rolled metal flanged structural shapes bent to arcuate shape with one flange having holes to receive bolts for fastening the corrugated metal, whereby the surface is a portion of a cylinder, such surface at its lower horizontal leading edge being spaced from one to three inches above the ground whereby to permit dirt and debris to blow under said leading edge.

8. The blast fence of claim 6, in which the corrugated material is formed of panels of galvanized steel, the blast deflecting surface is supported by a series of substantially parallel rolled solid steel bars of rectangular cross section, each bent to arcuate shape with the long axis of the rectangular section parallel to the blast direction, said uniformly curved bars of rectangular cross section containing holes adapted to receive fastening means by which the corrugated deflecting surface and the rear support struts may be fastened.

9. The blast fence of claim 6 in which the blast load is concentrated through each structural member to a pair of spaced concrete piers fitting cylindrical holes in said ground area, one hole of each pair being directly behind the other of that pair by a distance at least as great as the height of the fence, said piers being spaced between 36" and 48" apart spanwise along the fence; the diam eter of said piers being between 12" and 24" and of a depth between 12" and 24", the forward pier of each pair receiving the fastening means for securing the front end of the curved rearward support and the rear pier of that pair receiving the fastening means for securing the lower end of the rigid member, whereby such small piers eliminate the need for the much larger usual con crete platform extending all the way from the front of the fence to the rear supports of the struts, as the forward and rear distance between the piers is such as to eliminate the tendency of the fence to overturn upon receiving an exceptionally heavy blast.

10. Means for eliminating vibration due to local separation of supersonic high velocity blasts at elevated temperatures as from a military jet engine with afterburner as said blast is directed against a blast deflecting surface; which comprises a substantially impervious blast deflecting surface smoothly curved to be concave as viewed from the source of the blast with the curvature of said surface being such that a jet blast directed against the deflecting surface is directed upwardly from the upper discharge edge, said surface being of corrugated material with the corrugations running horizontally and normal to the jet blast, and a plurality of substantially vertical, curved supports engaging the corrugated material, the latter having its leading edge proximate the ground and its upper discharge edge located at the top of the fence in rear of the leading edge whereby a vortex generator effect is produced in the valleys of the corrugations causing a rolling type of reverse flow which slows down the layer adjacent the blast deflecting surface and thus eliminates local separation and the consequent vibration.

11. The means of claim 10 in which valleys of the corrugations are roughly three-quarters of an inch deep, the curved supports are supported by shoring struts anchored to the ground, and the shortest horizontal distance from the leading edge of the blast deflecting surface to the rear end of its strut is at least equal to the height of the discharge edge above ground.

References Cited in the file of this patent UNITED STATES PATENTS 1,026,806 Iblings May 21, 1912 2,974,910 Lynn Mar. 14, 1961 3,017,146 Wagner Jan. 16, 1962 3,037,726 Phillips June 5, 1962 

1. IN A BLAST FENCE ADAPTED TO BE INSTALLED ON A GROUND AREA TO RECEIVE AND DEFLECT THE BLAST FROM AN AIRCRAFT POWER UNIT OF THE JET TYPE WITH AFTERBURNER, MEANS FORMING A SUBSTANTIALLY IMPERVIOUS BLAST DEFLECTING SURFACE SMOOTHLY CURVED TO BE CONCAVE AS VIEWED FROM THE SOURCE OF THE BLAST, THE CURVATURE OF SAID SURFACE BEING SUCH THAT A JET BLAST DIRECTED AGAINST THE SURFACE IS DIRECTED UPWARD FROM THE UPPER EDGE OF THE FENCE, AND A DEFLECTING SURFACE SUPPORTING STRUCTURE; SAID MEANS BEING OF CORRUGATED MATERIAL WITH THE RIBS AND VALLEYS OF THE CORRUGATIONS IN HORIZONTAL PLANES AND HAVING A LEADING EDGE PROXIMATE THE GROUND AND AN UPPER DISCHARGE EDGE IN REAR OF THE LEADING EDGE; SAID SUPPORTING STRUCTURE COMPRISING A SERIES OF UNIFORMLY CURVED, SUBSTANTIALLY PARALLEL, ROLLED STEEL STRUCTURAL MEMBERS TO WHICH ARE SECURED AT CLOSELY SPACED INTERVALS ALONG THEIR LENGTHS, SAID CORRUGATED MATERIAL; EACH ROLLED STEEL STRUCTURAL MEMBER BEING SECURED TO THE GROUND AT ITS FORWARD LEADING END, AND BEING SECURED TO THE GROUND AT A SINGLE POINT BEHIND SAID LEADING END THROUGH A PORTION OF SAID SUPPORTING STRUCTURE COMPRISING AT LEAST ONE SLOPING SHORING STRUT FASTENED TO THE ROLLED STEEL MEMBER , WHEREBY THE PRESSURE OF THE BLAST IS TRANSMITTED UNIFORMLY TO THE GROUND AT TWO SPACED POINTS PER EACH ROLLED STEEL STRUCTURAL MEMBER, THAT IS, ONE POINT AT THE FRONT OF EACH ROLLED STEEL STRUCTURAL MEMBER AND THE OTHER POINT AT THE REAR OF EACH SLOPING SHORING STRUT, AND SAID HORIZONTAL ARRANGEMENT OF THE VALLEYS OF THE CORRUGATIONS PRODUCES A VORTEX GENERATOR EFFECT WHICH ELIMINATES VIBRATION. 